On loading and unloading container ships or other container-transporting means use is made of so-called twist locks, which are inserted in recesses at the corners of the containers for fixing the same to one another or to the stacking area.
There is clearly a need of rapidly fitting these twist locks, which do not form part of the containers, and then release them again from the container when not in use and to safely keep them in stock for the following use, so that they do not become dirty or lost. Thus, twist locks not correctly stored or placed in the operating area on the roadway used by large stackers constitute a hazard for the stacker tyres, because they can damage the same.
Hitherto part of this problem, namely the fitting using complicated devices such as are e.g. described in U.S. Pat. No. 6,688,249 B1 has been solved or, as is standard practice through the world in both small and large ports, by workers, who perform on the containers the corresponding manipulations such as removal, gripping and attaching when the containers are hanging at eye level on a crane.
The further problem exists that the workers can only move up to the container when it is stationary and before this the area at and around the container where lowering takes place is blocked. Moreover, hitherto the crane operator has had to estimate to what level he must lower the container so that it can be easily reached manually, whilst greatly reducing in stepwise manner the lowering speed.